1. Field of the Invention
The present invention relates to a temperature-programmed desorbed gas analyzing apparatus which is one type of thermal analyzing apparatus, and particularly to an improvement of a temperature programmed desorbed gas analyzing apparatus adopting a gas collecting system called as a skimmer interface system.
2. Description of the Related Art
The temperature-programmed desorbed gas analyzing method is a thermal analyzing method for measuring the amount of generated gas desorbed from a solid sample as a function of sample temperature when the temperature of the sample is increased at a preselected constant rate, and it is also called as TDS (Thermal. Desorption Spectroscopy) or TPD (Temperature Programmed Desorption).
The temperature-programmed desorbed gas analyzing method is carried out by using a temperature-programmed desorbed gas analyzing apparatus. Temperature-programmed desorbed gas analyzing apparatuses having various structures have been hitherto proposed, and a temperature-programmed desorbed gas analyzing apparatus adopting a gas collecting system called as a skimmer interface system is known as one of these temperature-programmed desorbed gas analyzing apparatuses.
This type of temperature-programmed desorbed gas analyzing apparatus is disclosed in “Journal of the Mass Spectrometry Society of Japan”, Vol. 46/No. 4, pp402–403 in 1998.
The apparatus disclosed by the above paper is equipped with a sample chamber 101 in which a sample is disposed, a heating furnace 102 for heating the sample, a measuring chamber 103 into which gas desorbed from the sample S by heating is introduced, a turbo molecular pump 104 for reducing the pressure in the measuring chamber 103, and a mass spectrometer 105 having a gas detector 105a (ion source) disposed in the measuring chamber 103 as shown in FIG. 4.
The inside of the sample chamber 101 is set to ambient pressure. An intermediate pressure-reduced chamber 106 is provided between the sample chamber 101 and the measuring chamber 103. A first orifice 107 is formed between the intermediate pressure-reduced chamber 106 and the sample chamber 101, and a second orifice 108 is formed between the intermediate pressure-reduced chamber 106 and the measuring chamber 103. Gas generated in the sample chamber 101 is collected through the orifices 107 and 108, and introduced into the measuring chamber 103.
The pressure in the measuring chamber 103 is reduced by the turbo molecular pump 104. When the inside of the sample chamber 101 is heated by the heating furnace 102, the temperature of gas existing in the sample chamber 101 is increased, and the gas kept at high temperature in the sample chamber 101 is introduced through the intermediate pressure-reduced chamber 106 into the measuring chamber 103. When the temperature of the gas introduced into the measuring chamber 103 is high, the pressure in the measuring chamber 103 is increased in proportion to the temperature of the gas. Therefore, the pressure in the measuring chamber 103 is increased although the turbo molecular pump 104 is activated to reduce the pressure in the measuring chamber 103, so that the detection sensitivity of the mass spectrometer 105 is reduced.
The reduction in sensitivity which is caused by temperature variation of gas introduced into the measuring chamber as described above has been hitherto treated as being within the range of an error.